Right. If the particle you're looking at has a very similar refractive index as air (or if the pile is in water, then the refractive index of water. Whatever medium your pile is in) then you are not likely to see any visible aberrations at all. This needs to be close like withing a millionth of a percent.

If your particle has a significantly different refractive index, but is still mostly transparent, then you are likely to see it clearly. Even if a contiguous mass would be near transparent, every time the light passes from one substance to the other (and a pile like this is likely to have millions of such interactions) then it will scatter a bit of light every time. You will see this most likely as a white powder.

The only other option is that the particle is not transparent. It either absorbs or reflects most visible light, in which case it will look like any other pile of stuff. It will take on the visual properties of that stuff. Except reflection might end up looking more scattered or matte than normal. As an example, a really shiny metal that you could see your reflection in when atomized is likely to lose the perfect surface finish that gives it that specular reflection where an image can be made out. It is going to reflect the light in all directions equally so it will just look like a pile of silver dust.